EP3451021B1 - Measuring device with scan functionality and adjustable receiving areas of the receiver - Google Patents

Description

The invention relates to a measuring device with scanning functionality for optically measuring an environment.

To detect objects or surfaces in an environment, methods are often used that scan using a laser scanner. The spatial position of a surface point is detected by measuring the distance to the targeted surface point using the laser and linking this measurement with angle information from the laser emission. From this distance and angle information, the spatial position of the detected point can be determined and, for example, a surface can be continuously measured. Often, in parallel to this purely geometric detection of the surface, an image is also recorded using a camera, which provides not only the overall visual view but also other information, e.g. regarding the surface texture.

3D scanning is a very effective technology for producing millions of individual measurement data, especially 3D coordinates, within minutes or seconds. Typical measurement tasks include recording objects or their surfaces such as industrial plants, house facades or historical buildings, but also accident sites and crime scenes. Surveying devices with scanning functionality include total stations or theodolites, which are used to measure or create 3D coordinates of surfaces. For this purpose, they must be able to direct the measuring beam - usually a Laser beam - of a distance measuring device over a surface or along an edge and thus to record successively in different measuring directions and simultaneously the direction and distance to the respective measuring points at a given scanning or measuring rate. Direction and distance are related to a measurement reference point such as the location or zero point of the surveying device, in other words they are in a common reference or coordinate system, so that the individual measuring directions and thus the individual measurement data are linked to one another via the local coordinate system. From the distance measurement value and the correlated measuring direction for each point, a so-called 3D point cloud can then be generated from the large number of scanned points, for example using an integrated or external data processing system.

Measuring devices with scanning functionality are also used as LiDAR systems, for example for airborne landscape surveying. Laser pulses from a moving carrier, in particular an aircraft or a drone (UAV, "unmanned aerial vehicle"), are sent to the surface via a quickly adjustable deflection element, e.g. a scanning mirror ("sweeping mirror") or a refractive optical component, according to a defined scanning grid. Based on returning parts of the radiation emitted to the surface and the carrier's own movement, for example recorded by means of a global navigation satellite system (GSNS) and/or by means of an inertial measuring unit (IMU), Thus, an accurate surface model of the surface to be measured can be derived.

Other measuring tasks of scanning measuring devices include, for example, monitoring an environment, for example as part of a warning or control system for an industrial production plant, or use in driver assistance systems.

Other applications of scanning measuring devices include, for example, determining the shape and area of tunnel cross-sections or determining the volume of excavation pits or gravel piles.

In the area of autonomous vehicles, the roads to be driven on are typically recorded in advance and mapped in a model. For example, vehicles equipped with scanners are used to scan and map the region in question. A LiDAR module used for this purpose, for example, has to meet special requirements for this task, particularly with regard to field of view and detection rate. For example, the horizontal field of view should cover around 80 degrees, although the required vertical field of view is typically much smaller, e.g. around 25 degrees. The detection rate for scanning the entire field of view is around 25 Hz, for example.

In terms of their basic design, such scanning measuring devices are designed, for example, with an electro-optical laser-based rangefinder to measure a distance to an object point as a measuring point, with a measuring direction deflection unit also being present. to vary the transmission direction of the distance measuring beam, for example with respect to one or more independent spatial directions, whereby a spatial measuring or scanning area can be covered.

Various principles and methods are known in the field of electronic or electro-optical distance measurement. One approach involves emitting pulsed electromagnetic radiation, such as laser light, at a target to be measured and then receiving an echo from this target as a backscattering object, whereby the distance to the target to be measured can be determined, for example, based on the travel time, the shape and/or the phase of the pulse. Such laser distance meters have now become standard solutions in many areas.

To detect the backscattered pulse or a pulse sequence, two different approaches or a combination thereof are usually used.

In the so-called threshold method, a light pulse is detected when the intensity of the radiation incident on a detector of the distance measuring device used exceeds a certain threshold. This threshold prevents noise and interference signals from the background from being falsely detected as a useful signal, i.e. as backscattered light from the emitted pulse.

However, it is problematic that in the case of weak backscattered pulses, such as those caused by larger measuring distances, detection is no longer possible if the pulse intensity falls below the detection threshold, ie below the threshold value. The main disadvantage of this threshold value method is that the amplitude of the measurement signal must be sufficiently larger than the noise amplitude of optical and electrical noise sources in the signal path in order to sufficiently minimize false detections, so that the threshold value method is only suitable to a limited extent for measurements at relatively large distances.

The other approach is based on sampling the backscattered pulse. This approach is typically used for weak backscattered signals (e.g. pulse signals), such as those caused by larger measurement distances. This method can also be viewed as holistic signal detection, whereby both the entire signal and the essential noise information are captured by sampling, which leads to an increase in measurement accuracy. An emitted signal is detected by sampling the radiation detected by a detector, identifying a signal within the sampled area and finally determining the position of the signal in time. By using a large number of samples and/or summing the received signal synchronously with the emission rate, a useful signal can be identified even under unfavorable circumstances, so that even larger distances or noisy or interference-affected background scenarios can be managed.

Nowadays, the entire waveform of the analog signal of the radiation detected by a detector is often sampled using the waveform digitizing method ("Waveform Digitizing", WFD). After identifying the coding of the corresponding transmission signal (ASK, FSK, PSK, also distance or interval modulation called, etc.) of a received signal, a signal propagation time ("pulse propagation time") is determined very precisely, for example by means of Fourier transformation or from a defined point in the sampled, digitized and reconstructed signal, such as the turning points, the curve maxima, or integrally by means of an optimum filter known from time interpolation.

Alternatively or in addition to determining the pulse transit time, (fast) sampling is often also carried out with regard to pulses or pulse sequences encoded or modulated in amplitude, phase, polarization, wavelength and/or frequency.

For example, in the approach of very precise temporal sampling or sampling of the backscattered signal, the electrical signal generated by the detector is converted into a digital signal sequence using an analog-digital converter (ADC). This digital signal is then usually further processed in real time. In a first step, this signal sequence is decoded by special digital filters (ASK, FSK, PSK, etc.), i.e. recognized, and finally the position of a signature describing a time interval within the signal sequence is determined. Examples of time-resolving signatures are the center of gravity, sine-cosine transformation or, for example, amplitude-normalized FIR filters (finite impulse response filters) with a set of weight coefficients derived from the pulse shape. In order to eliminate any distance drifts, a corresponding time-resolving signature is also compared with an internal start signal. In order to avoid irreversible sampling errors, additional digital signal transformations known to those skilled in the art are used.

One of the simplest types of modulation is the identification of individual pulses or pulse sequences by distance coding, as described in the EP 1 832 897 B1 . This is used, for example, for the purpose of re-identification. This recognition is necessary when an ambiguity arises, which can be caused by different situations when measuring the propagation time of pulses, for example when there is more than one pulse or group of pulses between the surveying device and the target object. Pulse coding is particularly advantageous in multi-beam systems consisting of several laser beams and associated receiving sensors.

The deflection unit can be implemented in the form of a moving mirror or alternatively by other elements suitable for the controlled angular deflection of optical radiation, such as rotatable prisms, movable light guides, light-refracting optical elements, deformable optical components, etc. The measurement is usually carried out by determining distance and angles, i.e. in spherical coordinates, which can also be transformed into Cartesian coordinates for display and further processing.

A scanning measuring device can in particular have two separate beam paths for the transmitting radiation and the receiving radiation, or the beam paths of the transmitting channel and the receiving channel can at least partially overlap. In particular, the beam paths can thus be designed in such a way that the deflection unit only acts on the transmitting radiation, ie that the imaging effect of the receiving channel is essentially independent of the control of a beam steering element. the deflection unit, that the transmitting channel and the receiving channel each have their own deflection unit, for example one that can be controlled separately, or that a single deflection unit acts on both the transmitting radiation and the receiving radiation.

If the deflection unit only acts on the transmitted radiation, this has the disadvantage that the imaging position of the received radiation on the receiver varies due to the varying angle of incidence and therefore a larger receiver surface is required than if, for example, the imaging position is stabilized using appropriate optics. However, the larger receiver surface also increases the background light component, which leads to a worse signal-to-noise ratio due to shot noise, for example. Such measuring devices are therefore typically used for measuring tasks where only a small solid angle range is to be scanned, so that the receiver surface can be kept small.

The background light component can be reduced, for example, by selecting the appropriate wavelength of the transmitted radiation and installing appropriate filters in the receiving path. However, this typically increases the complexity of the light source, as it must have a defined and stable wavelength. This is complex, requires special stabilization measures and also prevents, for example, a more compact design of the measuring device.

Especially for measuring tasks where larger solid angle ranges are to be scanned, the deflection unit is often arranged in such a way that The imaging position of the received radiation on the receiver is stabilized by the same beam steering element in the transmit and receive channels or by separate beam steering elements in the transmit and receive channels. This allows the receiver surface to be optimized, for example, with regard to the beam diameter of the middle receive beam and thus kept relatively small.

Especially in airborne LiDAR systems, the measurement distance to the earth's surface can be several kilometers (up to 5 km), whereby the angle adjustment rate of the deflection unit is relatively high (e.g. 200-300 rad/s). This leads, for example, to the setting of the deflection unit, e.g. the position of a single deflection mirror in a common beam path of the transmit and receive radiation, being different for an outgoing transmit signal and a corresponding incoming receive signal.

For example, the travel time for a pulse travelling at the speed of light (approx. 300,000 km/s) at a flight altitude of 5 km is 33 µs. With an angle adjustment rate of the deflection element common to the transmit and receive channels of 200 rad/s, this leads to a targeting error of 6.6 mrad. This means that the receiver looks 6.6 mrad away from the position where the laser beam hits the ground. If the laser beam has a beam diameter of, for example, 0.2-0.5 mrad, the field of view of the receiver must cover ten to twenty times the diameter of the laser beam in order to collect all the light coming back from the laser beam. If the LiDAR scanner can also execute a complex two-dimensional scanning grid, the targeting error occurs in all directions of the laser beam, which means The field of view requirement for the receiver is thus doubled again.

In order to keep the receiver small and thereby reduce the background light component, various methods are known in the state of the art to compensate for the targeting error due to the finite transit time as a function of the measuring distance, for example by means of distance-dependent control of complex optical compensation elements in the reception path. However, the individual solutions always require a compromise with regard to device parameters such as device size, system complexity, measurement accuracy, measurable distance range, or flexibility with regard to adjustable scanning patterns.

The EP 3 182 159 A1 describes both optical and sensor-based solutions for distance-dependent compensation of the aiming error to reduce the background light component in airborne distance measurement.

The object of the invention is to provide a measuring method or a measuring device which avoids the disadvantages known from the prior art, in particular enabling fast and precise measurements over an extended distance measuring range.

This object is achieved by implementing the characterizing features of the independent claims. Features that further develop the invention in an alternative or advantageous manner can be found in the dependent patent claims.

The invention relates to a measuring device for optically measuring an environment, comprising a radiation source for generating a transmission radiation, e.g. pulsed laser measuring radiation, a transmission channel for emitting at least a portion of the transmission radiation, a beam steering element in the transmission channel which is configured for deflecting the transmission radiation and for setting a time-varying transmission direction of the transmission radiation from the transmission channel, and a reception channel with a receiver which is configured to detect a reception signal based on at least a portion of the returning transmission radiation, hereinafter referred to as reception radiation. The measuring device further comprises control electronics which are configured to control the measuring device based on a pre-programmed measuring process, as well as an angle determiner for detecting angle data relating to the transmission direction of the transmission radiation, and a computing unit for deriving distance measurement data based on the reception signal. The measuring process carries out a scanning scan using the transmission radiation, based on a defined ongoing, in particular continuous, control of the beam steering element for the ongoing change of the transmission direction of the transmission radiation, the ongoing transmission of the transmission radiation and the ongoing detection of the reception signal, and the derivation of the distance measurement data.

According to the present invention, the receiver for detecting the received signal has an optoelectronic sensor based on an arrangement of microcells, in particular wherein the sensor is designed as an arrangement of single photon avalanche photodiodes, wherein the sensor has a plurality of microcells and is configured such that the microcells can be read individually and/or in microcell groups and thus individually readable active sub-areas of the receiver can be set. Readable means that the microcells or the microcell groups have a signal output which Determination of the transit time in picoseconds or subpicoseconds is permitted. As part of the measuring process, the control of the beam steering element and the detection of the received signal are synchronized in such a way that the detection of the received signal takes place based on an active sub-area of the receiver, wherein the active sub-area is set based on the angle data defining the transmission direction of the transmitted radiation and/or based on distance measurement data, in particular distance measurement data relating to an immediately preceding control of the beam steering element.

According to the present invention, the receiver therefore has a total detector surface, wherein a partial area of the total detector surface is set as an active detection area/an active partial area, wherein the active detection area can be adjusted in a time-variable manner with respect to its position on the total detector surface, in particular wherein the active detection area can also be adjusted in its shape and/or its extent, and wherein a receiver signal dependent on the setting of the active detection area is generated by reception radiation impinging on the total detector surface.

On the one hand, if the beam steering element only acts on the transmitted radiation, for example, a separate compensation must typically be provided on the receiving channel side with regard to the angle of incidence of the returning beam in the receiving channel, which varies due to the movement of the beam steering element. According to the invention, this compensation is therefore carried out on the detector side, based on the sensor according to the invention and depending on the transmission direction of the transmitted radiation.

On the other hand, if, for example, the imaging position of the received radiation on the receiver is stabilized by the same beam steering element in the transmit and receive channel or by separate beam steering elements in the transmit and receive channel, an angle difference occurs between the outgoing transmitted radiation and the received radiation with respect to the respective angle of incidence on the beam steering element due to the finite signal propagation time and the movement of the beam steering element, which results in the receiver looking away from the position where the laser beam hits the illuminated surface depending on the distance. This offset, which depends on the current distance, is compensated by the inventive use of the sensor.

The sensor can be an arrangement of single photon avalanche photodiodes, for example. Arrangements of single photon avalanche photodiodes, also called SPAD arrangements or SPAD arrays, are usually arranged as a matrix structure on a chip. The arrangements or chips with photosensitivity in the visible and near infrared spectral range are also known as SiPM (silicon photomultiplier). SiPMs are gradually replacing the photomultiplier tubes used to date, particularly in the visible and near ultraviolet spectral range. SiPMs have a high spectral sensitivity in the visible wavelength range. In the state of the art, for example, silicon-based SPAD arrays manufactured using CMOS technology are available that are sensitive up to the near infrared range up to wavelengths well over 900 nm.

The special feature of these SPAD arrays is their high amplification, which is why they have so far been used in very weak optical signals, where only 1 to 50 photons hit the sensor. Such sensors, for example airborne ones, are also called SPL-LIDAR (SPL = "single photon lidar"). However, with only a few photons, the distance noise is considerable and is typically 10 mm to 100 mm. In addition, the absolute distance measurement accuracy is influenced by the signal strength, especially in SPAD arrays with few microcells. By using special measures, such as range walk compensation, a distance noise of far less than 1 mm can be achieved, which achieves a measurement accuracy of 0.1 mm. This corresponds to a typical time resolution of one picosecond or less.

Commercial SPAD arrays are also available at wavelengths between 800 nm and 1800 nm. These sensors are mainly made of the semiconductor material InGaAs. Depending on the design, these sensors also have an external or internal matrix structure over the photo-sensitive area. Distance measurement systems with SPAD arrays in this spectral range have the advantage that the solar background light (daylight) is considerably lower than in the visible wavelength range and that this disturbing light flux therefore has less of an impact on the SPAD arrays.

The special feature of these SPAD array sensors is their very high photosensitivity, whereby the SPAD arrays are mainly designed to be able to detect individual photons perfectly. This is why they are also called "Multi Pixel Photon Counters" (MPPC). The SPAD arrays consist of hundreds, thousands, or even tens of thousands of microcells and are thus able to detect pulses with to receive thousands or hundreds of thousands of photons simultaneously. In addition, due to the parallel connection of the many microcells to cell groups (domains), there are still enough free cells for the signal photons even in solar background light.

Another special feature of SPAD arrangements is that individual microcells or individual subsets of microcells can be controlled separately and/or read out separately. The microcells can therefore be activated locally sequentially, for example for a row- or column-by-row reading of the receiver (e.g. as a "rolling shutter" or "rolling frame"). In particular, individually readable sub-areas of the receiver can be defined, depending on the direction of transmission.

For example, the sub-areas can be defined in such a way that they each represent a spatial sequence of neighboring microcells. However, the sub-areas can also be defined by spaced-apart areas of the receiver, i.e. the individual sub-areas do not represent a coherent sequence of microcells.

In particular, the individual sub-areas can be defined in such a way that they at least partially overlap each other.

For example, the sub-areas can be coordinated with one another in such a way that, through a sequence of signal acquisitions by individual sub-areas, for example, individual microcells or microcell groups (domains) of the SPAD arrangement can be alternately routed to the output , for example alternating even and odd rows (with respect to the SPAD arrangement) within the sub-areas. Such temporally alternating activation of microcells or microcell groups leads, for example, to a shortening of the recovery time of the SPAD array, which enables faster laser modulation or firing rate.

Instead of activating the microcells or microcell groups (domains) of the SPAD arrangement, they can remain activated in a stationary state, for example, in order to record and evaluate the outputs of the microcells or microcell groups (domains) synchronously with the scanning movement on the transmitter side for the "rolling shutter" or "rolling frame" function. In this case, the microcells or microcell groups (domains) that are aligned synchronously with the surface of the object that is illuminated by the transmitter-side laser are connected to the signal output using an electronic circuit, for example one integrated on the SPAD array. If the scanning movement of the laser moves in the vertical direction, the effective receiving-side domain shifts synchronously in the same direction, so that the (effective) field of view (FoV, "field of view") of the active receiving unit can receive the laser points on the object in a timely manner. The active FoV of the receiving unit is designed to be so small in the angular range that the backscattered received pulses can be completely viewed and received while receiving as little disturbing ambient light as possible.

According to the invention, direction-dependent active sub-areas are created depending on the direction of transmission of the transmitted radiation. of the receiver in order to adjust the receiver surface to a varying imaging position of the received radiation, for example to compensate for a targeting error due to the finite travel time and a rapidly rotating deflection mirror as a function of the measuring distance. This allows the receiver surface used to be optimized with respect to the incident received beam. For example, the active receiving surface can essentially be adjusted to the beam diameter of the respective received beam. This means that the background light component can be kept low for a single measurement even with a receiver that is actually oversized with respect to the beam diameter.

In contrast to the comparatively expensive photomultiplier tubes with large time jitter, modern SiPM sensors are inexpensive and have time jitter in the picosecond to sub-picosecond range. In addition, the SiPM arrays are manufactured using a conventional CMOS technology process, which also enables the integration of electronic components and circuits. The same applies to the SPAD arrays made of the semiconductor material InGaAs.

The high photosensitivity is due to the avalanche mechanism, whereby the individual microcells of the array are operated in the overvoltage range ("reverse voltage beyond the break voltage"), i.e. above the breakdown voltage at which a single photon triggers an avalanche of electrons, whereby the signal is greatly amplified depending on the setting, e.g. an amplification of up to a factor of one million. The current assigned to the photon is easy to convert into a voltage signal due to its strength. and feed it to a signal evaluation unit without significant amplification.

A SPAD array is capable of receiving several photons simultaneously, whereby the currents of the many microcells on the sensor chip can be added together and then converted into a voltage signal, for example via a resistor or a transimpedance amplifier. The SPAD array can be configured in such a way, for example with more than ten thousand microcells, that it behaves like an analog photosensor, whereby the characteristic curve is approximately proportional to the intensity of the incident laser pulse, for example with weak reception signals.

In the literature, a distinction is made between SPAD array operations in linear mode, Geiger mode and SPL mode (SPL, "Single Photon Lidar").

In linear mode below the breakdown voltage, a blocking voltage and temperature-dependent gain occurs and SPAD arrays can be used, for example, to construct highly sensitive photoreceivers with an output voltage proportional to the radiation power.

In Geiger mode and SPL mode, ie when operating above the breakdown voltage, SPADs and SPAD arrays can be used for single photon counting. In the Geiger mode, each individual pixel of the SPADs generates an output signal, with the electron avalanche being triggered by exactly one photon. If a photon packet consisting of several photons arrives, no larger signal is measured, so no amplitude information is available.

In Geiger mode, an incident photon packet generates only a (binary) event signal, which is not proportional to the number of photons in the photon packet.

SPL mode refers to a SPAD array operated in Geiger mode, where many microcells are connected in parallel to an output signal. When photon packets containing only a few photons arrive, the individual avalanches add up practically linearly and the amplitude of the output signal is therefore proportional to the number of photons detected.

The recovery time of the microcells after a photonic trigger is not zero but, for example, between 5-50 nanoseconds, which reduces the apparent sensitivity of the SPAD array for subsequently arriving photons. However, this has the advantage, for example, that the sensor can detect a signal strength range with high dynamics. This non-linearity is monotonic in SPAD arrays with a large number of microcells (>1000) and leads on the one hand to an amplitude compression between the input and output signal, and on the other hand to a weakened, increasing output signal as the input signal increases. Interestingly, the output signal of SPAD arrays with a high number of microcells (>1000) does not saturate completely, so that an amplitude change can be measured even with a received pulse with a very high number of photons of well over a million.

A SPAD array with a sufficient number of cells records the received signal amplitude over a large dynamic range and compresses the input amplitude of very small to very large signals. The SPAD array never overloads, even with very large signals, eg even when the radiation is reflected by an angle-precise retroreflector. With a photon number of 10 ⁹ , the output signal of the SPAD array asymptotically approaches a maximum limit voltage, this limit voltage is adapted to the subsequent amplifier circuit and guarantees that the subsequent electronics up to the time measurement circuit are not overloaded. This is what makes accurate distance measurement over a high dynamic range possible.

When measuring laser distances at different distances and varying surfaces, the number of photons can vary from less than 10 to more than 10 ⁹ . SPAD arrays, on the other hand, have a compression factor of the measured signal amplitude that is at least 10 ⁴ , typically 10 ⁸ , compared to the actual signal amplitude. SPAD arrays can therefore be used to measure both black diffuse targets and retroreflectors without the receiving unit requiring signal regulation. Due to the high amplification, SPAD arrays also have low noise, for example, and SPAD arrays with a high fill factor have a signal-to-noise ratio (SNR) that is suitable for distance measurements. The more microcells a SPAD array has, the greater the SNR.

The laser signals of a distance meter are usually pulse coded. Typical pulse rates are between kHz and GHz. Experiments have shown that such signals can be received well with SPAD arrays at voltages in overbreak mode. Pulse packets (bursts) can also be received clearly and almost noise-free with SPAD arrays. This is also the case when the recovery time of the microcells is quite long at ten nanoseconds. Due to the quasi-analog structure of SPAD arrays, a photocurrent present, for example, due to ambient light can also be received. The laser signal is then superimposed on the electrical photocurrent of the ambient light. For example, the current surge generated by the laser pulse at the output of the SPAD array is high-pass filtered so that the slow rear signal edge is shortened. The output pulse thus becomes a short signal pulse, e.g. with a pulse duration of less than one nanosecond. Such short pulses with steep edges are suitable for precise time and therefore also distance measurement. The use of a high-pass filter (differentiator), however, has no influence on the recovery time of the SPAD array.

Furthermore, initial attempts have already been made to integrate more electronic functionality into the SPAD arrays. For example, time measurement circuits ("TOF circuits") have already been assigned to each microcell. These measure the time of flight (TOF). For example, there are SPAD array implementations in which a precise photon count is integrated close to the microcells, which does not require a downstream analog-digital converter (ADC). In addition, a time measurement circuit (TDC, "time to digital converter") can be integrated in each microcell. A digital interface is also used as the output of the SPAD array. Such components are fully digital and do not require any "mixed signal processing" in CMOS production.

The receiving channel according to the invention enables the measuring device to achieve high scanning speeds by means of a fast movement of the beam steering element. On the receiver side, a measure is required that tracks the field of view (FoV, "field of view") of the receiving unit synchronously with the scanning on the transmitter side.

This measure consists, for example, in the fact that at a certain point in time only one domain, i.e. a subgroup of microcells of the SPAD array, is connected to the signal output, which is aligned exactly in the direction of the light spot on the object. Since the light spots are scanned over the object to be measured by the beam steering element, the active domain of the SPAD array is synchronously scanned over the object in a purely circuit-technical manner. This active domain of the SPAD array forms the active field of view of the receiving unit. This active field of view of the receiving unit is intentionally designed to be narrow so that as little sunlight as possible is captured and as few microcells of the active domain as possible are mistriggered. The activated sub-areas of the receiver move synchronously with the light spot over the surface of the SPAD array in such a way that the active microcells partially or completely enclose the light spot. This electronic scanning, also called "solid state scanning", eliminates the need for any moving parts on the receiving side, such as MEMS scanners, wedge scanners, polygon prism wheels or polygon mirror wheels.

According to the invention, the measuring device has an inertial meter which is configured to record inertial data relating to a movement of the measuring device, namely a tilt (6 degrees of freedom, 6DoF), and the active sensor used in the measurement process sub-area is selected based on the inertial data.

In particular, according to one embodiment, the measuring device is configured, for example, to detect a temporal progression of the measuring device's own motion and to estimate the measuring device's own motion in advance based on the temporal progression, wherein the active sub-area used in the measuring process is selected based on the estimated measuring device's own motion, in particular taking into account a temporal progression of initially derived distance measurement data.

For example, vibrations of the measuring device can be compensated, such as residual vibration of a gimbal-mounted measuring instrument in an aircraft.

The angle data regarding the transmission direction of the transmitted radiation are derived, for example, from control signals for controlling the beam steering element and/or based on angle measurement data which are provided, for example, by one or more angle gauges present in the measuring device.

According to a further embodiment, the measuring device is configured to derive an impact position of the received radiation on the sensor, in particular by means of determining the center of gravity or maximum of the detected received signal, and to derive correction information regarding the angle data based on the impact position and the distance measurement data.

For example, accurate referencing of distance measurement data for the creation of a point cloud can be achieved without the need for a protractor in the measuring device. For example, it may be sufficient if the (initially) derived angle data is based only on control signals for controlling the beam steering element and the initially derived angle data is corrected for referencing in a point cloud based on the impact position.

In a further embodiment, the measuring device is configured to estimate, based on the angle data, a first imaging information for a beam shape and/or position of the received radiation imaged on the receiver, in particular based on a defined fixed focus optics of the receiving channel, wherein the active sub-area used in the measurement process is selected based on the estimated first imaging information.

In particular, according to a further embodiment, the measuring device can be configured to estimate a second imaging information for a beam shape and/or position of the received radiation imaged on the receiver based on feedback from the receiver with respect to a previously detected received signal, wherein the active sub-area used in the measurement process is selected based on the estimated second imaging information.

According to a further embodiment, the measuring device is configured to estimate a third image information for a beam shape and/or position of the received radiation imaged on the receiver based on the distance measurement data, wherein the used active portion is selected based on the estimated third imaging information.

In one embodiment, the receiving channel is configured such that the imaging effect of the receiving channel is essentially independent of the control of the beam steering element, in particular wherein the beam steering element is arranged such that it only acts on the transmitted radiation. This means that the receiving channel has a static optical axis, i.e. no optical direction correction of the incident receiving beam takes place.

Alternatively, according to a further embodiment of the invention, the receiving channel can be configured, for example, such that the imaging effect of the receiving channel is dependent on the control of the beam steering element, which is arranged such that it also acts on the receiving radiation, so that a first deflection angle of the transmitted radiation and a second deflection angle of the received radiation are present depending on the control of the beam steering element. The measuring device is configured to estimate an angle difference between the first and second deflection angles based on an estimate of the time difference between the time at which the transmitted radiation passes the beam steering element and the time at which the associated received radiation passes the beam steering element, wherein the active sub-area used in the measurement process is set based on the estimated angle difference.

This means that, for example, a targeting error due to the finite transit time can be compensated as a function of the measuring distance, while at the same time the complexity of the optical structure can be kept low.

In particular, according to a further embodiment, the angle difference is estimated based on at least one element from a distance to a target object in the environment, in particular based on initially recorded distance measurement data, a setting rate of the time-varying transmission direction, a scanning pattern defined by the measuring process for the scanning scan by means of the beam steering element, and the inherent movement of the measuring device.

For example, the angle difference may be further estimated based on a continuous trend estimation based on previously estimated angle differences, in particular based on the last three immediately preceding angle differences.

Furthermore, according to a further embodiment, the receiver can have a plurality of sensors, wherein the plurality of sensors are arranged one-dimensionally or two-dimensionally relative to one another, in particular wherein each sensor has separate control electronics and/or evaluation electronics. In such arrangements of sensors, for example SPAD arrays, the individual arrays are often referred to as pixels, although each of these pixels itself consists of hundreds to tens of thousands of microcells.

Furthermore, according to a further embodiment, the receiver is designed such that a set of active sub-areas that can be read out in parallel is definable, in particular wherein the radiation source is configured to generate a bundle of differently directed and/or spaced laser measuring beams generated in parallel, wherein the subregions of the set of active subregions are defined in such a way that they are each assigned to a laser measuring beam of the bundle of laser measuring beams. This allows, for example, multibeam scanning to be carried out with several parallel and/or diverging laser measuring beams.

According to a further embodiment, the receiver has a blocking element on the receiving radiation side that is opaque to the receiving radiation, wherein the blocking element is configured such that a temporally variably adjustable passband is set for letting the receiving radiation through to the total detector surface of the receiver, wherein the position of the passband is adjustable with respect to the total detector surface, in particular wherein the passband is further adjustable with respect to its shape and/or its extent.

For example, the blocking element can be designed based on an adjustably rotatable disk arranged essentially parallel to the total detector surface, made of a material that is opaque to the receiving radiation and has an opening that is permeable to the receiving radiation. For example, the openings and the rotation speeds of two interlocking disks can be designed or adjusted in such a way that the transmission range can be adjusted in such a way that different transmission ranges have a define two-dimensional virtual movement across the detector surface.

The measuring device according to the invention is described in more detail below purely by way of example using embodiments shown schematically in the drawings. Identical elements are identified in the figures with the same reference numerals. The embodiments described are generally not shown to scale and are not to be understood as a limitation.

Fig. 1a-d:

exemplarische Anwendungsgebiete für das erfinderische Messgerät, z.B. a) luftgestützte LiDAR Vermessung, b) terrestrische LiDAR oder Scanner Vermessung, c) autonom fahrendes Fahrzeug, d) Totalstation;

Fig. 2:

schematische Illustration für eine Entstehung eines Anzielfehlers aufgrund der schnellen Bewegung eines Ablenkelements und der endlichen Laufzeit des Sendesignals;

Fig. 3a-d:

schematische Illustration eines Strahlengangs einer erfindungsgemässen Verwendung eines SPAD-Arrays als photosensitive Fläche eines Empfängers in einem Messgerät;

Fig. 4a,b:

erfinderische Ausführungsform ("Rolling Shutter Fenster") bezüglich der Definition der einzelnen von der Senderichtung abhängigen Teilbereiche der SPAD-Anordnung, z.B. a) eindimensional, b) zweidimensional;

Fig. 5:

Koordinatenmessinstrument mit zweistufigem Scanmechanismus basierend auf einem empfängerseitigen SPAD-Array;

Fig. 6a-b:

lineare Multipixelanordnung bestehend aus mehreren SPAD-Arrays für einen grosswinkligen Scanbereich.

In detail

Fig. 1a-d:

exemplary fields of application for the inventive measuring device, e.g. a) airborne LiDAR surveying, b) terrestrial LiDAR or scanner surveying, c) autonomously driving vehicle, d) total station;

Fig. 2:

schematic illustration of the occurrence of a targeting error due to the rapid movement of a deflection element and the finite propagation time of the transmitted signal;

Fig. 3a-d:

schematic illustration of a beam path of an inventive use of a SPAD array as a photosensitive surface of a receiver in a measuring device;

Fig. 4a,b:

inventive embodiment ("rolling shutter window") with respect to the definition of the individual sub-areas of the SPAD arrangement dependent on the transmission direction, e.g. a) one-dimensional, b) two-dimensional;

Fig. 5:

Coordinate measuring instrument with two-stage scanning mechanism based on a receiver-side SPAD array;

Fig. 6a-b:

linear multipixel arrangement consisting of several SPAD arrays for a large-angle scan area.

The Figures 1a to 1d show exemplary areas of application for measuring devices according to the invention with scanning functionality for detecting objects or surfaces in an environment by scanning with a laser measuring beam.

Figure 1a shows a typical airborne survey based on a LiDAR system on board an airborne carrier 1, e.g. an aircraft. A transmitted radiation 2 is generated, for example by short laser pulses, which is deflected towards the surface according to a defined scan pattern 3, for example by means of a movable mirror or by means of an adjustable refractive optical element. The surface is mapped, whereby the distance between the measuring device 4 and the associated surface points 5 is recorded for individual target directions of the transmitted radiation 2, for example by means of the pulse transit time method.

The measuring device 4 according to the invention can, for example, access further data for determining a relative or absolute position of the measuring device 4, for example inertial sensors 6 provided by the carrier 1, height measurement data, or data from a global positioning system 7. The measuring device 4, however, has also has its own inertial measuring devices for recording inertial data relating to the movement of the measuring device 4, e.g. a relative displacement and tilting of the measuring device 4. In addition, the measuring device 4 records, for example, at least the angles of the transmitter-side laser beam deflection units, whereby the relative or absolute position of the surface points 5 on the object to be measured is known.

The additional data can be partially processed by a computing unit 8 of the carrier or the computing unit 9 of the measuring device can be configured such that it processes the provided (raw) data directly, e.g. the computing unit 9 of the measuring device continuously derives the position and location of the measuring device 4 based on the data and, for example, generates a temporal progression of the proper movement of the measuring device 4.

The scan pattern on the object to be measured can be generated, for example, based on a simple "zig-zag" scan, e.g. by means of a back and forth moving ("sweeping") mirror and the forward movement of the airborne carrier 1. However, as shown in the figure, scan patterns 3 based on a circular scan ("Palmer scan") are often used, e.g. by means of a rotating inclined deflection mirror or by means of a refractive scanning unit. The flight movement thus creates a spiral-shaped scan pattern 3 on the surface to be measured. This has the advantage, for example, that each measured surface point 5 can be recorded from two different viewing angles in one flyover. This minimizes shadow effects, for example, and a large area can be scanned at the same time. In this embodiment, the optical receiving channel and the transmitting channel are routed via the same scanning elements such as deflection mirrors or polygon wheels.

According to the invention, the measuring device 4 has a receiver, for example based on a SPAD array, wherein direction-dependent partial areas of the receiver are defined depending on the transmission direction of the transmission radiation 2 in order to adjust the active receiver surface to a varying imaging position of the reception radiation 10, for example in order to compensate for a targeting error due to the finite transit time and a rapidly rotating deflection mirror as a function of the measuring distance.

Figure 1b shows a terrestrial application of a LiDAR system, designed for medium to large measuring distances, here for example in the area of construction monitoring, e.g. for monitoring or checking the integrity of a dam 11 by detecting the smallest movements of the dam 11 due to varying water pressure.

In terrestrial applications, the measurement distances are often shorter compared to airborne surveying, whereas the sampling rate can be significantly higher, e.g. due to the improved mechanical stability of the carrier 1 or due to the knowledge of existing 3D models of the surface to be measured, which allows, for example, already optimized sampling patterns to be used.

For example, the measuring device may be configured to measure a relatively small surface 12 of the dam with high scanning speed and high resolution, for example based on the pulse transit time principle, wherein a rapidly rotating mirror deflects the transmitted beam 2 along a first direction, for example to adjust the height, and the entire measuring system 4 is pivoted laterally (relatively slowly) back and forth about the axis of rotation 13.

According to the invention, the measuring device 4 has a receiver, for example based on a SPAD array, wherein direction-dependent active sub-regions of the receiver are defined depending on the transmission direction of the transmission radiation in order to adjust the receiver surface to a varying imaging position of the reception radiation 10.

For example, the receiver can be configured in such a way that the sub-areas used for detecting the received signal are in the sense of a "rolling shutter window" (see also Fig. 4 ) with the respectively set height of the corresponding transmission beam 2 on the receiver along the first direction "move up and down".

Figure 1c shows a further application of the measuring device 4 according to the invention in the field of autonomously driving vehicles, wherein, for example, the roads to be driven on are previously driven along by means of a vehicle 1 equipped with the measuring system 4 in order to record the roads and to depict the roads in a model.

Such systems typically require a robust and durable design of the measuring device 4, whereby typically a design as compact as possible is also sought and where Moving parts are avoided as much as possible. In addition, the measurement process has to meet special requirements, eg with regard to field of view and acquisition rate. For example, the horizontal field of view 14 should cover about 80 degrees, whereby the required vertical field of view 15 is typically much smaller, eg about 25 degrees. The acquisition rate for scanning the entire field of view is, for example, about 25 Hz.

MOEMS components ("micro-opto-electro-mechanical system") or adjustable or deformable refractive optical elements, such as liquid lenses, are therefore often used as deflection elements.

The inventive use of a receiver based on a SPAD array has the advantage, for example, that the optomechanical structure of the receiving channel can be simplified by the field of view of the SPAD array taking up the entire transmitter-side scanning area of 80 degrees x 25 degrees. As already described, however, only a small section of the receiver-side field of view is activated, namely the domain (activated group of microcells) that encloses the receiving light spot on the SPAD array. Alternatively, the slow horizontal movement of the measuring device 4 can also be guided on the receiver side via the transmitter-side directional deflection unit, for example, with the fast vertical scanning movement being carried out virtually on the receiver side, i.e. with a one-dimensional vertical activation of the domain on the SPAD array.

Figure 1d shows a use of the measuring device 4 according to the invention as a total station 16. Total stations are used, for example, to record properties of defined points in a measuring environment, in particular to record data with a spatial reference, ie direction, distance and angle to measuring points. Total stations therefore typically have alignment means for aligning the target axis 17 of the total station 16 with a target.

Total stations can also be designed for automatic target tracking, for example where a target is actively illuminated by emitted tracking radiation and identified and tracked based on the returning radiation, for example by detecting the placement of the detected tracking beam on a position-sensitive diode.

A total station 16 from the prior art has, for example, a base 18 and a support 19, wherein the support 19 is attached to the base 18 so as to be rotatable about a first axis of rotation 20. The total station 16 also has, for example, a carrier 21 which is attached to the support so as to be rotatable about a second axis of rotation 22 which is essentially orthogonal to the first axis of rotation 20, wherein the carrier 21 has an optical distance meter for measuring a distance to the target by means of a distance measuring beam 2. The carrier 21 also has, for example, a common exit and entry optics 23 for the emitted distance measuring beam 2 (transmission beam) and associated returning parts of the distance measuring beam 10 (reception beam). Alternatively, the carrier can also have separate entry optics and separate exit optics.

Typically, both the support 19 and the carrier 21 are moved for the two-dimensional alignment of the distance measuring beam 2 to a target, whereby for a specific measuring task, for example, at least one movement of the support 19 or the carrier 21 is necessary for each measuring process. Mainly the support 19, but also the carrier 21, are often comparatively heavy and thus sluggish components, which is why the scanning speed is correspondingly limited within the scope of a measuring task.

In order to increase the sampling rate, the carrier 21 therefore has, for example, an additional fast deflection element for the fast deflection 24 of the outgoing distance measuring beam 2 relative to the carrier 21. In this way, a fast movement of the beam of the distance measuring beam 2 required for the measurement can be achieved within the detection range of the entry optics 23 without requiring the otherwise necessary movement of the larger (sluggish) components. Points outside the detection range of the entry optics 23 are detected by means of a combined movement sequence. The slow or sluggish movements with low acceleration are carried out by means of the support 19 and carrier 21, the fast movements with high acceleration are carried out on the transmitter side by known means such as a polygon (prism or mirror), laser array or MEMS deflection means and on the receiver side by means of the inventive device.

According to the invention, the receiver of the distance meter is designed, for example, based on a SPAD array, wherein the control of the additional fast deflection element in the carrier 21 and the detection of the received signal are synchronized such that based on the transmission direction of the distance measuring radiation 2 (transmitted radiation) the received signal is detected based on a set active part of the receiver. On the receiver side, the fast scanning movement is again carried out virtually, i.e. with a one- or two-dimensional activation of the domain assigned to the light spot on the SPAD array.

Figure 2 shows a schematic illustration of the occurrence of a targeting error due to the rapid movement of a deflection element 25, here a fast moving (eg "sweeping") deflection mirror, and the finite propagation time of the transmission signal.

The transmission channel has a laser source 26, wherein the transmission radiation 2 generated by the laser source 26 is coupled into a common transmission and reception channel by means of a first fixed deflection element 27. Furthermore, a moving (e.g. "sweeping") deflection mirror 25 is located in the common transmission and reception channel, wherein the moving deflection mirror 25 acts on both the transmission radiation 2 and the reception radiation. The reception channel also has a second fixed deflection element 28, an imaging optics 29, and a LiDAR receiver 30 with a photosensitive reception surface 31.

Furthermore, on the one hand, optical main rays 32 are indicated with respect to a current targeting direction, ie a current setting 33 of the moving deflection mirror 25, and on the other hand, main rays 34 with respect to a previous setting 35 of the moving deflection mirror 25. For both orientations of the deflection mirror 25, the optical path between the LiDAR receiver and the deflection mirror 25 is static.

Due to the finite transit time of a transmitted and returned signal and the fast scanning rate using the movable deflection mirror 25, e.g. 300 rad/s, the orientation of the deflection mirror 25 has changed between the time of transmission of the transmitted radiation 2 and the time of return of the received radiation. This means that the received radiation is directed into the remaining (fixed) receiving optics at a (distance-dependent) angular offset. This means that the receiver looks away from the position where the laser beam hits the surface to be scanned with an offset depending on the measuring distance. The field of view of the receiver 30, or the receiver surface 31, must therefore cover, for example, a multiple of the diameter of the laser beam. If the LiDAR scanner can also execute a complex two-dimensional scanning grid, the aiming error occurs in all directions of the laser beam, which further increases the field of view requirement for the receiver 30. However, the larger receiver surface 31 also increases the background light component, which leads, for example, to a deteriorated signal-to-noise ratio.

According to the invention, the receiver surface 31 is designed, for example, as a SPAD array, wherein only the partial area which comprises the reflected laser spot is forwarded to the lidar receiving and evaluation unit.

The Figures 3a to 3d show schematically an inventive use of a SPAD array 36 as a photosensitive surface of a receiver. The Figures 3a,3b refer to a first transmission direction 37, set by a deflection element 38, which essentially only acts on the transmission radiation 2, ie the optical axis of the receiving channel is essentially static, and the Figures 3c,3d refer to a second transmission direction 39, set by the deflection element 38.

Figure 3a shows a side view of a simplified optical path for the first transmission direction 37, with a main axis 40 of a common exit/entrance optics 41 and a receiver having a SPAD array 36. The deflection element 38 can deflect the transmitted radiation 2 in particular one-dimensionally or two-dimensionally, ie along a first and/or second deflection direction. Furthermore, it is clear to a person skilled in the art that depending on the type of deflection element 38 used, e.g. mirror element, prism, polygon wheel, double wedge, refractive element, movable light guide or MOEMS component, and the mode of operation of the beam deflection achieved thereby, e.g. displacement/tilting of the deflection element or electro-optical control of optical (e.g. refractive) properties of the deflection element, this can be arranged in both a parallel and a divergent beam path.

Figure 3b shows a top view of the receiver, or rather the SPAD array 36 from Figure 3a According to the invention, the SPAD array 36 has a plurality of microcells and is configured in such a way that the microcells can be read individually and/or in microcell groups (domains) and thus individually readable sub-areas of the SPAD array 36 can be set. The control of the deflection element 38 and the detection of the reception beam 10 are synchronized in such a way that based on the transmission direction, here the first transmission direction 37, the reception beam 10 based on a defined sub-area of the SPAD array 36, here a first sub-area 42.

In an analogous way, the Figures 3c (side view) and 3d (top view) the optical path with respect to the second transmission direction 39, wherein a second partial region 43 for detecting the reception beam 10 is defined based on the second transmission direction 39.

In particular, the respectively defined active sub-areas 42, 43 can each be optimized with respect to the beam shape of the incident receiving beam 10. For example, the area of the sub-area can be essentially matched to the beam diameter of the respective receiving beam 10, whereby, for example, changes in the light spot size due to a fixed focus optics on the receiver side are taken into account. The background light component can thus be kept low for a single measurement even with a receiver that is in itself oversized with respect to the beam diameter.

Figure 4a shows a further inventive embodiment with regard to the definition of the individual active sub-areas of a sensor designed as a SPAD arrangement 36, which are dependent on the direction of transmission. The sub-areas are defined here in a similar way to a so-called "rolling shutter" principle, i.e. the location-dependent sub-area, which acts in a direction-dependent manner via the optics, is defined by a combination of several SPAD lines, whereby the sub-area "rolls" up and down over the SPAD array 36 in a direction perpendicular to the SPAD lines, depending on the current direction of transmission, similar to a rolling shutter window 45 whose height 44 is variable. This definition of sub-areas has, for example, the Advantage of simplified control electronics, whereby, for example, the height 44 of the current partial area 45 can be adapted to the beam diameter of the received radiation 10, e.g. as a function of a distance-dependent change in the light spot size.

A SPAD array configured in this way is suitable, for example, if the beam deflection by the deflection element 38 (see Fig.3a ) is deflected essentially one-dimensionally, ie along a deflection direction corresponding to the "rolling direction".

Furthermore, the measuring device can be configured, for example, in such a way that an impact position 46 of the received radiation 10 on the receiver, or the SPAD arrangement 36, can be derived, e.g. by determining the center of gravity or maximum of the received signal. The impact position 46 derived in this way allows the current active partial area 45 to be finely adjusted to the beam diameter of the received radiation 10 in real time. In addition, the associated transmission direction can be derived using the derived impact position 46 and the corresponding distance measurement data, for example in order to check angle data relating to the transmission direction, e.g. based on control signals from the deflection element 38, or to derive correction information relating to the angle data if necessary.

Figure 4b shows the receiving surface of a SPAD arrangement 36 with an active sub-area 45 which is dependent on the transmission direction and which moves in a two-dimensional direction. The movement track 48 of the light spot 10 on the SPAD array 36 and thus the path of the active sub-area 45, i.e. the active microcells, which moves as a domain in a scanning path over the surface of the SPAD array 36. Here too, the respective sub-areas are assigned to a direction of the transmission unit. If the direction of the transmission beam moves, for example, in the form of a serpentine line 48, the active sub-area 45 moves synchronously in a similar manner on the SPAD arrangement 36.

Figure 5 shows a measuring device according to the invention as a total station 16. The instrument is equipped here with a two-stage scanning mechanism, based on a first rotation axis 20 for rotating the support 19 with respect to the base 18, a second rotation axis 22 for rotating the carrier 21 with respect to the support 19, and at least one fast scanning deflection element in the carrier, which can additionally deflect the transmitted beam 10 at high angular velocity.

In the figure, a scan pattern 3 in the object space is shown as a movement track 48, wherein the S-shaped path is generated in a first part T ₁ only by rotations of the support 19 and/or the carrier 21 about the first 20 and second 22 axes. In a second part T _2, the movement track 48 is generated by means of the additional fast-scanning deflection element in the carrier 21, whereby a denser area coverage is achieved. This causes, for example, a more even distribution of the point density on the object surface to be scanned, especially at very high distance measurement rates of more than 1 MHz. Without the fast-scanning deflection element, the measuring points 52 would lie close to one line of the movement track 48, but measuring points would be between the lines. On the receiver side, a fast tracking of the field of view is also required. The inventive sensor is used, for example, for the Figures 4a and 4b described, an active sub-area 45 ( Fig. 4a,b ) in one-dimensional or two-dimensional direction, so that the signal of the associated laser emission from a group of microcells can be transmitted in a time-resolved manner to a distance measuring device.

Figures 6a and 6b show two further inventive embodiments of a photosensor unit suitable for so-called "solid state scanning". In Figure 6a The photosensor unit consists of several SPAD arrays 36 arranged in a line. This arrangement is suitable, for example, for scanning larger angular ranges in the object space. The received laser spot 10 moves across the several SPAD arrays. The active partial area 45 is moved in time and location synchronization with the received light spot 10 so that the measurement signal is received efficiently, but at the same time as little ambient light as possible is recorded per microcell. The displacement of the partial area 45 appears as a virtual movement 47 and is indicated in the direction of the arrow. The achievable field of view 50 of the receiving unit can be easily dimensioned using the number of SPAD arrays 36.

In Figure 6b Several SPAD arrays 36 are shown in a two-dimensional multi-pixel arrangement. Each pixel is its own SPAD array 36. The achievable field of view 50a,b is shown here as an example based on a 3x3 arrangement of individual SPAD arrays 36. In order for the If the total detection area has no gaps, SPAD arrays without edge areas can be used, for example. In this example, the movement of the received laser spot 10 describes a circular path 48, wherein the active partial area 45 encloses the laser spot 10 and is controlled in such a way that it moves with the laser spot 10 along a virtual scanning direction 47. If the microcell domain 45 is located entirely on a SPAD array, then the received signal of all microcells within the domain 45 is output to a single output signal line; if, however, the microcell domain 45 covers two neighboring SPAD arrays, then two output signal lines are activated, which can then be combined outside the multipixel SPAD array arrangement via a multiplexer circuit. This signal combination electronics can, however, also be implemented directly on the SPAD array pixels 36 (SPAD array chips), for example.

It is understood that these figures only schematically represent possible embodiments. The various approaches can also be combined with each other and with prior art methods.

Claims (13)

1. Measuring device (4) for optically surveying an environment, comprising

   - a radiation source (26) for generating transmitted radiation (2),

   - a transmitting channel for emitting at least a part of the transmitted radiation,

   - a beam deflection element (38) in the transmitting channel, which is configured to deflect the transmitted radiation (2) and to set a chronologically varying transmission direction (37, 39) of the transmitted radiation (2) out of the transmitting channel,

   - a receiving channel comprising a receiver (30), which is configured to acquire a reception signal based on at least a part of the returning transmitted radiation, referred to hereafter as received radiation (10),

   - a control electronics unit, which is configured to control the measuring device (4) based on a preprogrammed measurement procedure,

   - an angle determining unit for acquiring angle data with respect to the transmission direction (37, 39) of the transmitted radiation (2), and

   - a computer unit (9) for deriving distance measurement data based on the reception signal, wherein scanning is carried out by means of the transmitted radiation (2) by way of the measurement procedure, based on

   - a defined ongoing actuation of the beam deflection element (38) for the ongoing change of the transmission direction (37, 39) of the transmitted radiation (2),

   - an ongoing emission of the transmitted radiation (2) and an ongoing acquisition of the reception signal, and

   - a derivation of the distance measurement data, wherein

   - the receiver (30) for acquiring the reception signal has an optoelectronic sensor (36) based on an assembly of microcells,

   - the sensor (36) has a plurality of microcells and is configured such that the microcells can be read out individually and/or in microcell groups and active sections (42, 43, 45), which can be read out individually, of the receiver (30) are thus settable, and

   - in the scope of the measurement procedure, the actuation of the beam deflection element (38) and the acquisition of the reception signal are synchronized such that

   - the acquisition of the reception signal takes place based on an active section (42, 43, 45) of the receiver (30), wherein

   - the active section (42, 43, 45) is set based on the angle data defining the transmission direction (37, 39) of the transmitted radiation (2) and/or based on distance measurement data,
   characterized in that

   - the measuring device (4) has an inertia meter which is configured to acquire inertia data with respect to an intrinsic movement of the measuring device (4) that is a tilt, and

   - the active section (42, 43, 45) used in the scope of the measurement procedure is selected based on the inertia data.
2. Measuring device (4) according to claim 1, characterized in that

   the measuring device (4) is configured

   - to acquire a time curve of the intrinsic movement of the measuring device (4), and

   - to estimate the intrinsic movement of the measuring device (4) in advance based on the time curve,

   wherein the active section (42, 43, 45) used in the scope of the measurement procedure is selected based on the estimated intrinsic movement of the measuring device (4), in particular in consideration of a time curve of initially derived distance measurement data.
3. Measuring device (4) according to any one of the preceding claims,
   characterized in that
   the measuring device (4) is configured

   - to derive a position of incidence (46) of the received radiation (2) on the sensor (36), in particular by means of focal point determination or maximum determination of the acquired reception signal, and

   - to derive an item of correction information with respect to the angle data based on the position of incidence (46) and the distance measurement data.
4. Measuring device (4) according to any one of the preceding claims,
   characterized in that
   the measuring device (4) is configured, based on the angle data, to estimate a first item of imaging information for a beam shape and/or location of the received radiation (10) imaged on the sensor (36), in particular based on a defined fixed focus optical unit of the receiving channel, wherein the active section (42, 43, 45) used in the scope of the measurement procedure is selected based on the estimated first item of imaging information.
5. Measuring device (4) according to any one of the preceding claims,
   characterized in that

   the measuring device (4) is configured

   - based on feedback of the sensor (36) with respect to a previously acquired reception signal, to estimate a second item of imaging information for a beam shape and/or location of the received radiation (10) imaged on the sensor (36),

   wherein the active section (42, 43, 45) used in the scope of the measurement procedure is selected based on the estimated second item of imaging information.
6. Measuring device (4) according to any one of the preceding claims,
   characterized in that

   the measuring device (4) is configured

   - based on the distance measurement data, to estimate a third item of imaging information for a beam shape and/or location of the received radiation (10) imaged on the sensor (36),

   wherein the active section (42, 43, 45) used in the scope of the measurement procedure is selected based on the estimated third item of imaging information.
7. Measuring device (4) according to any one of the preceding claims,
   characterized in that
   the receiving channel is configured such that the imaging effect of the receiving channel is substantially independent of the actuation of the beam deflection element (38), in particular wherein the beam deflection element (38) is arranged such that it acts solely on the transmitted radiation (2) .
8. Measuring device (4) according to any one of claims 1 to 6,
   characterized in that

   - the receiving channel is configured such that the imaging effect of the receiving channel is dependent on the actuation of the beam deflection element (38), which is arranged such that it acts on the received radiation (10), and therefore dependent on the actuation of the beam deflection element (38), a first deflection angle of the transmitted radiation (2) and a second deflection angle of the received radiation (10) are provided, and

   - the measuring device (4) is configured to estimate an angle difference between the first and second deflection angles, based on an estimation of the time difference between the point in time of the passage of the beam deflection element (38) by the transmitted radiation (2) and the point in time of the passage of the beam deflection element (38) by the associated received radiation (10),

   wherein the active section (42, 43, 45) used in the scope of the measurement procedure is set based on the estimated angle difference.
9. Measuring device (4) according to claim 8, characterized in that
   the angle difference is estimated based on at least one element of

   - a distance to a target object in the environment, in particular based on initially acquired distance measurement data,

   - a setting rate of the chronologically variable transmission direction (37, 39),

   - a scanning pattern (3) defined by the measurement procedure for the sweeping scanning by means of the beam deflection element (38), and

   - the intrinsic movement of the measuring device (4) .
10. Measuring device (4) according to any one of claims 8 to 9, characterized in that
    the angle difference is estimated based on a continuously occurring trend estimation on the basis of previously estimated angle differences, in particular based on the last three immediately preceding angle differences.
11. Measuring device (4) according to any one of the preceding claims,
    characterized in that
    the receiver (30) has multiple sensors (36), wherein the multiple sensors are arranged one-dimensionally or two-dimensionally in relation to one another, in particular wherein each sensor (36) has a separate actuation electronics unit and/or analysis electronics unit.
12. Measuring device (4) according to any one of the preceding claims,
    characterized in that

    the receiver (30) is designed such that a set of active sections (42, 43, 45) which can be read out in parallel with respect to time is definable,

    in particular wherein the radiation source (26) is configured

    - to generate a bundle of differently oriented and/or spaced-apart laser measuring beams generated in parallel, and

    - the sections (42, 43, 45) of the set of active sections are defined such that they are each associated with a laser measuring beam of the bundle of laser measuring beams.
13. Measuring device (4) according to any one of the preceding claims,
    characterized in that

    - the receiver (30) has a radiation-opaque blocking element for the received radiation (10) on the received radiation side,

    - the blocking element is configured such that a transmission region settable in a chronologically variable manner is set to transmit the received radiation (10) to the overall detector surface of the receiver (30), wherein

    - the position of the transmission region is settable with respect to the overall detector surface, in particular wherein the transmission region is furthermore settable with respect to its shape and/or its dimensions.

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